title: Isolation and characterization of a putative multidrug resistance pump from Vibrio cholerae.
abstract: Multidrug-resistant strains of Vibrio cholerae (the causative agent of the diarrhoeal disease cholera) have recently been described. In an attempt to identify a homologue of the Escherichia coli TolC in V. cholerae, we isolated a DNA fragment (pVC) that enabled an E. coli tolC mutant to grow in the presence of 0.05% deoxycholate (DOC). However, other TolC defects were not complemented. Nucleotide sequence analysis of this fragment revealed the presence of two open reading frames (ORF1 and ORF2) separated by 9 bp and encoding 42.4 and 55.8 kDa proteins respectively. The translational products of these two ORFs correlated closely with the molecular weights of the predicted proteins. The deduced amino acid sequences of ORF1 and ORF2 showed a high degree of similarity with conserved regions of the E. coli efflux pump proteins, EmrA and EmrB. The presence of pVC2 within the E. coli efflux pump mutants defective in either the emrAB or the acrAB genes provided the mutants with resistance against several antibiotics. A V. cholerae isogenic mutant defective in ORF2 was constructed by gene replacement. Characterization of this mutant has shown it to be more sensitive to CCCP, PMA, PCP, nalidixic acid and DOC than the parent strain. These results suggest that ORF1 and ORF2 constitute an operon encoding two components of a putative multidrug resistance pump in V. cholerae. In addition, the presence of both structural and functional similarities between VceAB and EmrAB suggests that VceAB is a homologue of EmrAB.
authors.affiliation: Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock 79430, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Colmer
authors.forename: J A
authors.initials: JA
authors.lastname: Fralick
authors.forename: A N
authors.initials: AN
authors.lastname: Hamood
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000737:chemistry; D018432:Drug Resistance, Multiple / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016366:Open Reading Frames; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014734:Vibrio cholerae / Q000737:chemistry* / Q000187:drug effects / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; C489681:EmrA protein, E coli; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C489682:VceA protein, Vibrio cholerae; C077168:emrA protein, Bacteria; C077169:VceB protein, Vibrio cholerae